A structure has been conventionally known, in which: a pair of left and right front side frames are provided at a vehicle body front portion, or a pair of left and right rear side frames are provided at a vehicle body rear portion; and a bumper beam extending in a vehicle width direction is attached to tip end portions of these side frames through a pair of left and right crash cans (also called crush boxes) capable of absorbing impact energy in collision.
The pair of crash cans are typically molded by a metal material. In vehicle collision, the pair of crash cans cause compression fracture in an axial direction to absorb impact energy transmitted to a vehicle interior.
It is also known that since the crash can is a large component, the crash can is constituted by a fiber-reinforced resin molded body for the purpose of a weight reduction of a vehicle body.
Examples of the reinforced fiber used as a reinforcing member include a glass fiber, a carbon fiber, and a metal fiber. The fiber-reinforced resin is formed by combining the reinforced fibers with a base material (matrix).
According to such fiber-reinforced resin, the reinforced fibers take charge of dynamic characteristics, such as strength, and the base material resin takes charge of a stress transmission function between the fibers and a fiber protection function.
Especially, carbon fiber resin (Carbon-Fiber-Reinforced-Plastic: CFRP) has both high specific strength (strength/specific gravity) and high specific rigidity (rigidity/specific gravity), so to speak, both lightness and strength or rigidity. Therefore, the carbon fiber resin is widely used as a structural material for aircrafts, vehicles, and the like.
An impact energy absorber structure of a vehicle body of PTL 1 includes an impact energy absorber made of fiber-reinforced resin and supported by a front suspension member module provided at a front side of the vehicle interior. The impact energy absorber is formed to have a substantially U-shaped vertical section and integrally includes: a bottom wall portion extending in a forward/rearward direction and a leftward/rightward direction; and left and right vertical wall portions extending upward from both respective left and right end portions of the bottom wall portion. Each of the bottom wall portion and the left and right vertical wall portions is formed in a corrugated plate shape and includes a plurality of concave and convex portions extending in the forward/rearward direction. With this, a difference between a figure center of the impact energy absorber and a height of a floor panel is reduced, and this reduces a bending moment acting on the floor panel.
According to a vehicle body structure of PTL 2, an impact energy absorber made of fiber reinforced plastic and having a square tube shape and an opening direction that is an upper/lower direction is provided at a front surface side of a vehicle body structural body, and a bumper is arranged at a front surface of the impact energy absorber. With this, both the weight reduction and the energy absorbing property are achieved.
Performance required for impact absorbing members such as the crash can is a large energy absorption amount (hereinafter referred to as an EA amount) and a stable absorption of impact energy by progressive fracture in which compression fracture proceeds progressively.